This invention pertains generally to methods and apparatus employed to remotely view welding processes on-line and more particularly to such methods and apparatus as are applicable to arc welding processes.
A major difficulty exists in monitoring arc welding processes due to the extremely high contrast range between the arc and the surrounding environment. This problem becomes particularly difficult when remote monitoring is desired. For high quality control of the weld it is extremely advantageous to be able to see the arc, the surrounding metal and the welding pool while the welding operation is in progress. Remote monitoring is particularly desirable where the welding application is performed remotely in a hostile environment, such as in nuclear steam generators.
Previously, in order to directly view the arc during the welding process welders generally employed a protective helmet having a smoked viewing lens which attenuated light over the entire visual spectrum, and thus failed to enhance the contrast ratio between the arc and its surroundings which masked most of the details of the process. Where remote systems were employed special filtering arrangements such as the system taught in U.S. Pat. No. 4,021,840 issued May 3, 1977 were provided to screen out infrared and ultraviolet radiation while passing visible light reflected from the workpiece unattenuated, for the purpose of avoiding overloading cameras used to view the process.
One possible approach to reduce the contrast ratio would be to flood the area surrounding the welding arc with light. However, the amount of light required to produce an acceptable contrast ratio is extremely high and incandescent white light sources in excess of one kilowatt beamed directly on the area have shown negligible improvement.
Accordingly, an improved apparatus and method for viewing an arc welding process is desired that will reduce the contrast between the arc and its surroundings and provide a high definition image amenable to remote viewing.